Combined Approaches to Predict Microplastic Emissions Within an Urbanized Estuary (Warnow, Southwestern Baltic Sea)

Abstract

Microplastic river emissions are known to be one of the major sources for marine microplastic pollution. Especially urbanized estuaries localized at the land-sea interface and subjected to microplastic emissions from various sources exhibit a high microplastic discharge potential to adjacent coasts. To adapt effective measures against microplastic emissions a more detailed knowledge on the importance of various microplastic sources is necessary. As field data is scarce we combined different approaches to assess microplastic emissions into the Warnow estuary, southwestern Baltic Sea. Resulting microplastic emission estimates are based on in-situ measurements for the catchment emissions, whereas for the remaining microplastic sources within the estuary literature data on microplastic abundances, and various parameters were used (e.g. demographical, hydrological, geographical). The evaluation of the different emission scenarios revealed that the majority of microplastic is likely discharged by the Warnow river catchment (49.4%) and the separated city stormwater system (43.1%) into the estuary, followed by combined sewer discharges (6.1%). Wastewater treatment plant emissions exhibit the lowest percentage (1.4%). Our approach to estimate anti-fouling paint particles emissions from leisure and commercial shipping activities was associated with highest uncertainties. However, our results indicate the importance of this source highlighting the necessity for future research on the topic. Based on our assumptions for microplastic retention within the estuary, we estimate a potential annual emission of 152–291 billion microplastics (majority within the size class 10–100 µm) to the Baltic Sea. Considering all uncertainties of the different applied approaches, we could assess the importance of various microplastic sources which can be used by authorities to prioritize and establish emission reduction measures. Additionally, the study provides parameters for microplastic emission estimates that can be transferred from our model system to other urbanized Baltic estuaries.

Measuring impacts of microplastic treatments via image recognition on immobilised particles below 100 μm

“…Large reference libraries containing spectra of large varieties of paint composites preferably from different manufacturers might be able to detect paint flake MP based on their (pigment dominated) fingerprint. This approach has also been taken by other studies [13,51]. Most pigments are, however, not solely applied in synthetic polymers but in a large diversity of technical applications, which is why an indirect identification of MP via those pigments cannot be done in a systematic way.…”

Emission, Transport, and Deposition of visible Plastics in an Estuary and the Baltic Sea—a Monitoring and Modeling Approach

“…As soon as heavy rain exceeds the hydraulic capacity of the combined sewer system, storm-and wastewater are entering the estuary largely without treatment. According to Piehl et al (2021), the total annual amounts emitted to the estuary were about 41 million m³ stormwater, 107,065 m³ combined sewer overflow water and 16.5 million m³ treated wastewater.…”

“…Emissions of microplastic with waste-and stormwater from the city are addressed and documented in Piehl et al (2021). The emission of visible plastics via these pathways can hardly be estimated based on literature and calculations, because visible plastics can have multiple sources and can stem from fragmentation.…”

“…All minor riverine systems are part of the Rostock city drainage system. Piehl et al (2021) analyzed microplastics emissions to the Warnow Estuary (based on very few data) and assumed that more than 1/3 of the total emissions enter with the river. This means that the river potentially can be an important source for large micro-and mesoplastics, as well.…”

Addressing the importance of microplastic particles as vectors for long-range transport of chemical contaminants: perspective in relation to prioritizing research and regulatory actions

“…While research implies a variety of competing processes that influence the environmental fate and transport of MPs, from which it may initially appear are challenges that would be near-impossible to characterize and quantify, there are potentially opportunities to leverage learnings from other areas of research. Research aimed at characterizing and quantifying the vertical and horizontal transport of particulate organic matter (POM), for instance, may represent insight that could be readily applied towards understanding the mass flux of MPs from rivers to the marine environment [34,61,[65][66][67]. As noted by Harris [61], however, few studies reporting on MPs in the aquatic environment actually report the sedimentation rate associated with the system being monitored for MPs.…”